Sterilization of a fluid by ultraviolet radiation

ABSTRACT

A device for sterilizing water or another fluid, including a flexible bag through which the fluid is pumped and formed of a material transparent to ultraviolet radiation, with the bag extending first along one side of an ultraviolet lamp or lamps and then being doubled back along their opposite sides; and with the bag being pressed against the lamps by the pressure of the fluid being treated in a manner causing an inner wall of the bag to conform approximately to the shape of the lamp or lamps and thereby enhance or optimize the delivery of radiation to the fluid.

United States Patent Veloz Aug. 8, 1972 [72] Inventor: Louis P. Veloz, 500 South Madison,

Pasadena, Calif. 15701 22 Filed: June30,1970

21 Appl.No.:51,065

[52] US. Cl. ..250/43, 21/102, 119/5, 250/48 [51] Int. Cl .JIOI] 37/00 [58] Field of Search ....250/43, 44, 45, 86, 51; 119/5; 21/102 [56] References Cited UNITED STATES PATENTS 3,535,513 10/1970 Cirami ..250/43 3,551,091 12/1970 Veloz ..250/43 3,447,892 6/1969 Watson ..250/51 Primary Examiner-James W. Lawrence Assistant Examiner-C. E. Church Attorney-William P. Green [57] ABSTRACT A device for sterilizing water or another fluid, including a flexible bag through which the fluid is pumped and formed of a material transparent to ultraviolet radiation, with the bag extending first along one side of an ultraviolet lamp or lamps and then being doubled back along their opposite sides; and with the bag being pressed against the lamps by the pressure of the fluid being treated in a manner causing an inner wall of the bag to conform approximately to the shape of the lamp or lamps and thereby enhance or optimize the delivery of radiation to the fluid.

20 Claims, 7 Drawing Figures so, 2 I8 24 2'2 0'2 33 PATENTEDms' 8 1972 3,683,177

sum 1 BF 2 INVENTOR. L s P. YELOZ PATENTEDAUG 8 I972 sum 2 or 2 LOU/S P. V54

Q firm/2 EV STERILIZATION OF A FLUID BY ULTRAVIOLET RADIATION BACKGROUND OF THE INVENTION This invention relates to improved devices for sterilizing water or another fluid by subjection to ultraviolet radiation. Though the invention in its broadest aspects is applicable to the sterilization of fluids for any of various different purposes, certain particular features of the invention are especially useful for sterilizing the water of an aquarium. To simplify and clarify the disclosure, the invention will be discussed primarily as applied to that use.

In an aquarium, the bacteria count in the water builds up very rapidly to an unacceptable level unless some means are provided for destroying or removing the bacteria. Among other means heretofore proposed for this purpose, it has been suggested that ultraviolet radiation be employed. However, though ultraviolet radiation is basically a very efiective and convenient way to sterilize water, the devices thus far suggested for utilizing such radiation to treat aquarium water have had certain distinct disadvantages rendering them essentially unacceptable for actual practical use. For example, in some of these prior devices the ultraviolet lamps have been directly immersed within a stream of water, in a manner introducing the danger of electrocution of the fish, and of persons touching the equipment. This hazard has been a very real one which prevents such equipment from passing the safety codes of many cities and other jurisdictions. Further, in those previously proposed types of aquarium sterilizing units which have been so devised as to overcome this electrocution hazard, the structures utilized in attempting to achieve this result have reduced the sterilizing effectiveness of the ultraviolet equipment so drastically that it becomes essentially worthless for the purpose; One such arrangement employs a flat quartz window between the lamp, and the water, but inherently by its structure permits use of radiation emitting from the bulb through only a very small angle, and therefore is very inefficient insofar as its use of the total emitted radiation is concerned.

SUMMARY OF THE INVENTION The present invention provides a unit which, in an extremely simple overall structure, is capable of completely eliminating all danger of electrocution, and at the same time attains maximum efliciency and effectiveness by directing through the fluid being treated substantially all of the radiation emitting in all directions from an ultraviolet lamp or lamps. Thus, lamps of very low wattage may be employed, and by continuous recirculation of the water within the aquarium can maintain that water continuously at a very low bacteria count level.

To achieve these results, I preferably employ a container or conduit through which the fluid being treated is passed, and having a wall which is exposed to radiation from an ultraviolet lamp, and is adapted to pass that radiation through the wall and into the fluid stream. In order to optimize the transmission of the will pass through the conforming flexible radiationtransparent wall and into the fluid. For maximum simplicity, the container or conduit may be formed as a flexible bag or series of bags, whose side walls are forced against the lamp or lamps by the pressure of the fluid being treated.

In a presently preferred arrangement, an elongated bag of this type extends first along one side of an ultraviolet lamp or lamps, and then curves back along the opposite side of the lamps, and upon application of pressure to the contained liquid is forced against the opposite sides of the lamps to substantially completely encircle them in an optimum fluid irradiating relationship. The bag may be contained within a confining housing, which supports the bag externally in its proper position, and which is formed of a. material opaque to the harmful radiation in ultraviolet light, to prevent escape of any of that radiation from the device.

This housing or a wall thereof may be transparent, however, to visible light, so that a pleasing blue light in the visible spectrum may pass from the device into the water of the aquarium to illuminate it in an attractive manner. The preferred material for forming the flexible bag or flexible wall is tetrafluoroethylene polymer (Teflon), which will pass substantially one hundred percent of the sterilizing radiation, but to which none of the bacteria or other impurities in the water will adhere, to thus maintain the bag clean and freely transparent to the radiation for a very extended period of time.

BRIEF DESCRIPTION OF THE DRAWING The above and other features and objects of the invention will be better understood from the following detailed description of the typical embodiment illustrated in the accompanying drawing in which:

FIG. 1 is a perspective view of a home aquarium having a water sterilizing unit constructed in accordance with the invention;

FIG. 2 is an enlarged vertical section taken on line 2-2 of FIG. 1;

FIG. 3 is a transverse vertical section taken on line 3-3 of FIG. 2;

FIG. 4 is a horizontal section taken on line 4-4 of FIG. 2;

FIGS. 5 and 6 are views taken in the vertical planes 5-5 and 6-45 respectively of FIG. 2; and

FIG. 7 is an exploded perspective view showing in separated condition the various difierent portions of the sterilizing unit.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1, I have shown at 10 a conventional rectangular home aquarium, having four vertical glass or plastic side walls 11 and a bottom wall, and containing a body of water 12 within which fish and/or other sea life are contained. The usual water circulating pump 13 is mounted on a back wall of the aquarium, as by hangers or hooks 14 extending over the top edge of the back wall. This pump takes suction from the water in the aquarium through a hose l5, and is energized by electrical power from a supply line 16 to pump water slowly through an outlet hose 17 to a sterilizing unit 18 embodying the present invention.

This unit 18 ultimately discharges the water through a hose 19 which extends over the upper edge 20 of the rear wall 11. and then downwardly into the aquarium. Pump 13 may contain a built-in filter unit which removes particulate matter from the water before delivery to sterilizing unit 18.

Sterilizer 18 has a housing 21 including an upper housing section 22 and a lower housing section 23. Upper section 22 carries two downwardly projecting ultraviolet lamps 24 which sterilize water pumped through a flexible bag or conduit 25 located in and supported by the bottom housing section 23.

The upper section 22 of the housing may form a rectangular enclosure or chamber 122, defined by two parallel horizontal top and bottom walls 26 and 27, two parallel vertical inner and outer walls 28 and 29, and two parallel vertical opposite end walls 30 and 31 disposed perpendicular to walls 28 and 29. Top wall 26 may be rectangular, and projects inwardly beyond the plane of vertical inner wall 28, to form a horizontal projection 32 which extends over the upper edge of rear wall 11 of the aquarium, and which carries a downwardly projecting lip 33 for engaging the inner surface of the rear wall 11 of the aquarium in a manner effectively supporting the entire sterilizer 18 in the position illustrated in H6. 1. The outer wall 29 of upper section 22 of the housing is rectangular and projects downwardly beneath the level of bottom wall 27 of the upper housing section, and to a lower horizontal edge 34 of wall 29 lying in essentially the same horizontal plane as the undersurface 35 of bottom section 23 of the housing. This downwardly projecting portion 36 of outer wall 29 is opaque to both visible and ultraviolet radiation, to shield the back side of lower housing section 23 against emission of radiation in that direction. Similarly, all of the other walls 26, 27, 28, the rest of wall 29, walls 30 and 31 are desirably all opaque to both visible and ultraviolet radiation, to enclose and shield from view within compartment 122 the electrical ballast 36 and the upper portions of the sockets 37 and 38 into which ultraviolet lamps 24 are threadedly connectible.

The ballast 36 and sockets are for best results secured to outer vertical side wall 29 of the upper section 22 of housing 21. For this purpose, ballast 36 may have two aligned planar mounting flanges 39 received against the inner side of wall 29, and secured rigidly thereto by fasteners 40, typically screws or rivets. At its underside, ballast 36 may carry a horizontal socket mounting plate 41, secured in any convenient manner to the ballast, with sockets 37 and 38 then being rigidly secured to the underside of rigid plate 41 as by screws 44. An electrical power line 45 is connectible to house current (preferably 110 volt, 60 cycle alternating current), and extends into the interior of the upper section of the housing through a rubber grommet 46 connected into an opening in wall 3i, with the power line being connected within compartment 122 to the ballast and sockets in the conventional series relationship.

The sockets 37 and 38 have downwardly projecting tubular externally substantially cylindrical portions 47 which are centered about parallel vertical axes 48, and project downwardly through circular openings 49 in bottom wall 27 of the upper section of the housing. These sockets contain internal threads centered about the axes 48 and into which the upper threaded ends of the bulbs 24 are connectible.

In order to allow access to the interior of the upper hollow section of housing 21, for repair or replacement of the electrical parts, it is desirable that that upper housing section be formed in two parts appropriately secured together and adapted to be separated when desired. For this purpose, the previously discussed upper wall 26 and outer wall 29, as well as the downwardly projecting lip 33 on wall 26, may all be formed together as a first part of the upper housing section, while the remaining walls 27, 28, 30, and 31 may be formed as a second housing part, with this second part being securable to the first part by screws 50 extending through apertures in walls 30 and 31 and connecting into lugs or shoulders 51 projecting downwardly from top wall 26. If these two screws 50 are detached and bulbs 24 are removed from their sockets, the second part of the upper section of the housing may be removed downwardly from the upper part consisting of walls 26 and 29, to allow access to the sockets and ballast. The wires connecting line 45 to the sockets and ballast may be sufficiently long or loose to enable such movement of grommet 46 and the wall by which it is carried relative to the sockets and ballast.

The lower section 23 of housing 21 is of the essentially rectangular configuration illustrated in FIG. 7, having a horizontal rectangular bottom wall 53, two parallel vertical rectangular inner and outer walls 54 and 55, and two parallel vertical opposite end walls 56 and 57. Outer wall is received adjacent and parallel to the downwardly projecting shield portion 36 of outer wall 29 of upper section 22. inner wall 54 of lower section 23 is aligned vertically with the inner wall 28 of the upper section of the housing. The upper edges 62 and 63 of inner and outer walls 54 and 55 of the lower section extend parallel to one another and horizontally, and are engageable upwardly against the underside of bottom wall 27 of the top section, when the two sections are secured together in the normal FIG. 1 relationship. To attach the two sections together in the above manner, the opposite end walls 30 and 31 of the upper section may have downwardly projecting resilient tabs 58 containing rectangular openings 59 within which detent lugs 60 on coacting resilient upwardly projecting tabs 61 carried by the end walls 56 and 57 of the lower housing section are receivable in snap detenting relation.

The bag or conduit 25 through which water to be sterilized is pumped, may be considered as taking the form essentially of an elongated tube formed of freely flexible film or sheet form material which is transparent to ultraviolet radiation, or at least to the wave lengths of such radiation which are capable of destroying bacteria (2000 to 2600 angstroms wave length). This tubular bag 25 extends from a first end 64 thereof longitudinally at 65 within the interior of lower housing section 23 and along the first side of the two lamps 24, and then forms a reverse bend at 66 adjacent the second end of the housing to curve back at 67 along the opposite side of the lamps to the second end 68 of the tube. At its two ends 64 and 68, the tube 25 may be cemerited continuously and peripherally to the outer surfaces of two plastic connector elements 69 and 70, each of which extends a short distance into the corresponding end of the tube to allow such cementing to the tube in a permanently sealed relation. The two fittings 69 and 70 are received adjacent one of the end walls 56 of lower section 23 of the housing, and carry two short integrally formed horizontally projecting tubes 71 and 72 which extend out of the housing through notches 73 and 74 formed at opposite sides of one of the upwardly projecting detent tabs 61. The inlet and outlet hoses 17 and 19 of the sterilizer are then connected to these tubes 71 and 72 at the outside of the housing.

As seen in FIGS. 5 and 6, the connector elements 69 and 70 at opposite ends of tube 25 are elongated vertically, and therefore tend to give the tube 25 a correspondingly vertically extending cross-sectional shape, so that the tube may easily be received within the spaces between lamps 24 and the vertical side and end walls of the lower section of the housing. Tube 25 thus has a generally vertical inner wall 75 received adjacent the lamps, and a generally vertical outer wall 76 received adjacent the side walls and one end wall of the housing. The vertical height of tube and its end pieces 69 and 70 is desirably approximately the same as the vertical height of the compartment formed within the lower section 23 of the housing.

As indicated previously, the film or sheet material from which tube 25 is formed is a substance capable of passing at least the sterilizing portion of the ultraviolet radiation; .and preferably is also a material to which bacteria and other impurities in the water will not tend to adhere. For best results, this material forming tube or bag 25 is a thin film of a fluorocarbon polymer, preferably polytetrafluoroethylene, as sold by E. I. Du- Pont de Nemours under the trade name Teflon (FEP type). The film desirably has a thickness between about 2 and 3 mils, and for best results about 2 mils.

To now describe the manner of use of the discussed sterilizing device, assume that the unit 18 has been mounted on the side wall of an aquarium as illustrated at 10 in FIG. 1, and that it has been connected to the aquarium and a pump 13 in the manner of FIG. 1. If both the pump and sterilizer are now energized electrically, the pump will commence to draw water from the aquarium through line 15, and discharge it through line 17 into one end of the tubular bag 25. This water flows longitudinally within the bag, first along one side of the two lamps 24, and then back along the opposite side of the lamps to ultimately discharge through line 19 into the aquarium.

The pressure produced by pump 13 is great enough to force the inner initially generally vertical wall 75 of tube or bag 25 inwardly against the lamps 24, as seen in FIGS. 2, 3 and 4 and with a force sufficient to cause the flexible wall 75 to conform closely to, and preferably substantially exactly to, the outer essentially spherical shape of each of the lamps 24. Thus, at each side of each lamp, the bag forms a substantially hemispherical recess containing and closely receiving a side of the inwardly at their upper sides far enough to contact the lamp sockets entirely about their peripheries, so that no portion of the lamp surfaces is left free of contact with a corresponding portion of the flexible bag wall. By virtue of this highly eflicient relationship between the flexible bag and the lamps, the radiation is utilized so eflectively that lamps of very small wattage (e. g., 4 watts each) can under continuous circulation conditions maintain an entire aquarium at an extremely low bacteria count level.

The confinement of the water being treated within flexible bag 25 eliminates any danger of electrocution such as may occur when the lamps are immersed directly in the water. To further increase the safety of the apparatus, bottom wall 53 of the lower section 23 of the housing is provided with openings 78 at its four comers to allow drainage from the housing of any water which may leak from bag 25. Thus, even if a leak were to develop in the bag, the water would immediately run out of the housing section 23, and could not contact the electrical connections to the lamp sockets. To

assure such drainage of the water, the openings are made large enough to drain water by gravity from section 23 at a rate at least as great as, and preferably greater than, the rate at which pump 13 delivers water to the sterilizer. Further, it is preferred that the entire sterilizing unit, including bag 25 and the housing compartment within which it is contained, be located above the level of the water in the aquarium tank 10, to additionally insure against any tendency for immersion of the lamps in water under any possible conditions.

It has previously been noted that the upper section 22 of housing 21 is formed of a material opaque to both ultraviolet and visible radiation. The lower section 23 of the housing is, on the other hand, preferably formed of a material which, while opaque to ultraviolet radiation of the bacteria-destroying wave lengths, is nevertheless transparent to visible light. As a result, the small amount of violet and blue light in the visible range which is normally produced by an ultraviolet lamp can pass through the walls of the lower housing section 23 and into the aquarium, to give the water and contents of the aquarium a very attractive appearance. A suitable substance having this characteristic of not transmitting the undesired ultraviolet light while transmitting visible light may be an appropriate transparent acrylic material, such as methylmethacrylate. If desired, the inner wall 62 of lower housing section 23 may be formed of this type material to pass blue light into the interior of the aquarium, while the other walls of the lower housing section may be formed of a material opaque to both visible and ultraviolet light.

The tubular bag 25 may be formed of an initially flat sheet of material folded to a tubular shape and seamed longitudinally. In order to facilitate attachment of the opposite ends of the tube to fittings 69 and 70, the

the end of the housing in a relation closing off the flow of liquid at that point. For this purpose, the bag 75 may be initially formed as a simple tube in which the overall horizontal lengths of walls 75 and 76 between their opposite ends are identical, but with outer wall 76 subsequently being stretched longitudinally (horizontally) at 66, to the desired increased length greater than that of wall 75. In operation, when the pressure within tube 25 forces the inner wall 75 inwardly against the lamps, the same pressure forces the outer wall 76 outwardly against the vertical walls of the lower housing section 23, so that the tube then is externally essentially rectangular in shape, and internally of a shape corresponding to the configuration of the two lamps 24.

If it becomes desirable to clean or replace the bag 75, the pump may first be stopped and then lower housing section 23 may be easily released for downward separation from the upper housing section, by pressing inwardly on and thereby releasing detent tabs 61. As section 23 is moved downwardly, it carries with it the bag 75, which may then be easily removed from section 23 through its open upper side for cleaning or replacement.

While a certain specific embodiment of the present invention has been disclosed as typical, the invention is of course not limited to this particular form, but rather is applicable broadly to all such variations as fall within the scope of the appended claims.

I claim:

1. A sterilizer comprising at least one lamp adapted to produce ultraviolet radiation, a container through which a fluid to be sterilized is passed and having a wall exposed to said radiation formed of a material through which the radiation will pass into the fluid to sterilize it, said wall being flexible and being positioned to be urged against said lamp by said fluid and to conform approximately in shape to a portion of the lamp in a relation enhancing transmission of radiation to the fluid.

2. A sterilizer as recited in claim 1, in which said wall is formed of a flexible film of tetrafluoroethylene polymer.

3. A sterilizer as recited in claim 1, in which said container is a flexible bag extending along a first side of the lamp and then doubled back to return along its opposite side and having said wall in engagement with and conforming in shape approximately to opposite sides of the lamp.

4. A sterilizer as recited in claim 1, including a housing having a portion extending about and holding said container.

5. A sterilizer as recited in claim 1, including a body structure carrying said lamp, and a housing holding said container and detachably connectible to said body structure in a position locating said flexible wall of the container adjacent the lamp.

6. A sterilizer as recited in claim 1, in which said lamp projects downwardly, and said container is a generally U-shaped flexible bag having a first portion extending along one side of the lamp and then doubled back to form a second portion extending along the opposite side of the lamp, with the lamp projecting downwardly between said portions.

7. A sterilizer as recited in claim 1, including a housing having an upper hollow first section and a lower hollow second section, means for securing said lower section of the housing detachably to said first section, a socket mounted to said upper housing section and carrying said lamp in downwardly projecting position, said container being a generally U-shaped flexible bag contained in said lower housing section and having two portions between which said lamp is receivable.

8. A sterilizer as recited in claim 7, in which said wall of the bag engages and conforms at least partially to both of two opposite sides of the lamp.

9. A sterilizer as recited in claim 1, including a housing which said container is located and having a wall which is opaque to ultraviolet radiation but is adapted to pass visible light from said lamp to the exterior of the housing for illuminating an associated aquarium.

10. A sterilizer as recited in claim 1, including a housing having a first section which carries said container and is opaque to ultraviolet radiation but transparent to visible light to pass visible light from said lamp to the exterior of said first section at a first side, said housing including a second section having a wall which is opaque to visible light and is received at a second side of the first section as a shield.

11. A sterilizer as recited in claim 1, including a housing structure carrying said lamp and said container and having a mounting portion adapted to hook over the upper edge of an aquarium wall to hang the sterilizer thereon.

12. A sterilizer as recited in claim 1, including a housing having a first section carrying said lamp and a second section carrying said container, and interfitting snap detents on said two sections for releasably securing them together in a sterilizing condition.

13. A sterilizer as recited in claim 1, including a housing having an upper hollow first section with a mounting portion adapted to hook over and be supported by the wall of an aquarium, a socket carried by said first housing section and carrying said lamp in downwardly projecting position, said housing having a lower hollow second section, releasable detents on said two sections for securing said second section detachably to the underside of said first section, said container being a generally U-shaped bag of flexible tetrafluoroethylene polymer which extends along a first side of said lamp and then doubles back along the opposite side thereof and which conforms approximately in shape to opposite sides of the lamp, a ballast for said lamp in said first housing section, said second section being formed of a substance which'is opaque to ultraviolet but transparent to visible light, said lamp producing some visible light which passes to the exterior of said lower section at a first side thereof to enter an associated aquarium, said upper section being formed of a material opaque to visible light and forming a shield opaque to such visible light and projecting downwardly at a second side of the first section.

14. A sterilizer comprising a housing, a flexible bag contained in and supported by said housing and having a flexible wall adapted to pass ultraviolet radiation, inlet and outlet means for conducting a fluid to be sterilized through said bag, and at least one ultraviolet lamp positioned to pass ultraviolet radiation through said wall and into said fluid to sterilize it, said flexible wall of said bag being positioned to be urged against said lamp by said fluid.

l5. A sterilizer as recited in claim 14, in which said bag is generally U-shaped and extends first along one side of said lamp and is then doubled back along the opposite side of said lamp.

16. A sterilizer as recited in claim 14, in which said housing has a drain opening through which any leakage from the bag may escape to the exterior of the housing.

17. A sterilizer as recited in claim 14, in which said housing has an upper section carrying said lamp and a lower section carrying said bag and secured detachably to the upper section.

18. A sterilizer as recited in claim 14, in which said housing has an upper section carrying said lamp and a lower section carrying said bag and secured detachably to the upper section, said lower section having a wall opaque to ultraviolet but transparent to visible light, said upper section having a wall which is opaque to visible light projecting downwardly along an outer side of the lower section.

19. A sterilizer as recited in claim 14, in which said bag first extends along one side of said lamp and is then doubled back in a return bend to extend along the opposite side of the lamp, said bag having inner and outer walls the latter of which is longer than the former to avoid closure of the fluid passage through the bag at said return bend.

20. The method of manufacture that comprises forming a tubular bag of flexible material adapted to pass ultraviolet radiation, positioning said bag to extend first along one side of an ultraviolet lamp and then be doubled back in a return bend to extend along the opposite side of the lamp, and at some time during said method stretching an outer wall of said bag to a greater length than an inner wall thereof to avoid closure of the bag at said return bend by contact of said inner wall with said outer wall. 

1. A sterilizer comprising at least one lamp adapted to produce ultraviolet radiation, a container through which a fluid to be sterilized is passed and having a wall exposed to said radiation formed of a material through which the radiation will pass into the fluid to sterilize it, said wall being flexible and being positioned to be urged against said lamp by said fluid and to conform approximately in shape to a portion of the lamp in a relation enhancing transmission of radiation to the fluid.
 2. A sterilizer as recited in claim 1, in which said wall is formed of a flexible film of tetrafluoroethylene polymer.
 3. A sterilizer as recited in claim 1, in which said container is a flexible bag extending along a first side of the lamp and then doubled back to return along its opposite side and having said wall in engagement with and conforming in shape approximately to opposite sides of the lamp.
 4. A sterilizer as recited in claim 1, including a housing having a portion extending about and holding said container.
 5. A sterilizer as recited in claim 1, including a body structure carrying said lamp, and a housing holding said container and detachably connectible to said body structure in a position locating said flexible wall of the container adjacent the lamp.
 6. A sterilizer as recited in claim 1, in which said lamp projects downwardly, and said container is a generally U-shaped flExible bag having a first portion extending along one side of the lamp and then doubled back to form a second portion extending along the opposite side of the lamp, with the lamp projecting downwardly between said portions.
 7. A sterilizer as recited in claim 1, including a housing having an upper hollow first section and a lower hollow second section, means for securing said lower section of the housing detachably to said first section, a socket mounted to said upper housing section and carrying said lamp in downwardly projecting position, said container being a generally U-shaped flexible bag contained in said lower housing section and having two portions between which said lamp is receivable.
 8. A sterilizer as recited in claim 7, in which said wall of the bag engages and conforms at least partially to both of two opposite sides of the lamp.
 9. A sterilizer as recited in claim 1, including a housing within which said container is located and having a wall which is opaque to ultraviolet radiation but is adapted to pass visible light from said lamp to the exterior of the housing for illuminating an associated aquarium.
 10. A sterilizer as recited in claim 1, including a housing having a first section which carries said container and is opaque to ultraviolet radiation but transparent to visible light to pass visible light from said lamp to the exterior of said first section at a first side, said housing including a second section having a wall which is opaque to visible light and is received at a second side of the first section as a shield.
 11. A sterilizer as recited in claim 1, including a housing structure carrying said lamp and said container and having a mounting portion adapted to hook over the upper edge of an aquarium wall to hang the sterilizer thereon.
 12. A sterilizer as recited in claim 1, including a housing having a first section carrying said lamp and a second section carrying said container, and interfitting snap detents on said two sections for releasably securing them together in a sterilizing condition.
 13. A sterilizer as recited in claim 1, including a housing having an upper hollow first section with a mounting portion adapted to hook over and be supported by the wall of an aquarium, a socket carried by said first housing section and carrying said lamp in downwardly projecting position, said housing having a lower hollow second section, releasable detents on said two sections for securing said second section detachably to the underside of said first section, said container being a generally U-shaped bag of flexible tetrafluoroethylene polymer which extends along a first side of said lamp and then doubles back along the opposite side thereof and which conforms approximately in shape to opposite sides of the lamp, a ballast for said lamp in said first housing section, said second section being formed of a substance which is opaque to ultraviolet but transparent to visible light, said lamp producing some visible light which passes to the exterior of said lower section at a first side thereof to enter an associated aquarium, said upper section being formed of a material opaque to visible light and forming a shield opaque to such visible light and projecting downwardly at a second side of the first section.
 14. A sterilizer comprising a housing, a flexible bag contained in and supported by said housing and having a flexible wall adapted to pass ultraviolet radiation, inlet and outlet means for conducting a fluid to be sterilized through said bag, and at least one ultraviolet lamp positioned to pass ultraviolet radiation through said wall and into said fluid to sterilize it, said flexible wall of said bag being positioned to be urged against said lamp by said fluid.
 15. A sterilizer as recited in claim 14, in which said bag is generally U-shaped and extends first along one side of said lamp and is then doubled back along the opposite side of said lamp.
 16. A sterilizer as recited in claim 14, in which said housing has a drain opeNing through which any leakage from the bag may escape to the exterior of the housing.
 17. A sterilizer as recited in claim 14, in which said housing has an upper section carrying said lamp and a lower section carrying said bag and secured detachably to the upper section.
 18. A sterilizer as recited in claim 14, in which said housing has an upper section carrying said lamp and a lower section carrying said bag and secured detachably to the upper section, said lower section having a wall opaque to ultraviolet but transparent to visible light, said upper section having a wall which is opaque to visible light projecting downwardly along an outer side of the lower section.
 19. A sterilizer as recited in claim 14, in which said bag first extends along one side of said lamp and is then doubled back in a return bend to extend along the opposite side of the lamp, said bag having inner and outer walls the latter of which is longer than the former to avoid closure of the fluid passage through the bag at said return bend.
 20. The method of manufacture that comprises forming a tubular bag of flexible material adapted to pass ultraviolet radiation, positioning said bag to extend first along one side of an ultraviolet lamp and then be doubled back in a return bend to extend along the opposite side of the lamp, and at some time during said method stretching an outer wall of said bag to a greater length than an inner wall thereof to avoid closure of the bag at said return bend by contact of said inner wall with said outer wall. 